state 加税题！i need your help

one state adds a 7 percent sales tax to the price of most products purchased within its jurisdiction. This tax, therefore, if viewed as tax on income, has the reverse effect of the federal income tax: the lower the income, the higher the annual percentage rate at which the income is taxed.

The conclusion above would be properly drawn if which of the following were assumed as a premise?

A) the amount of money citizens spend on products subject to the state tax tends to be equal across income levels.

B) the fedral income tax favors citizens with high incomes, whereas the state sales tax favors citizens with low incomes.

C) citizens with low annual incomes can afford to pay a relatively higher percentage of their incomes in state sales tax, since their federal income tax is relatively low.

D)the lower a state's sales tax ,the more it will tend to redistribute income from the more affluent citizens to the rest of society.

E) citizens who fail to earn federally taxable income are also exempt form the state sales tax.

正确答案是A， i am totally confused, 大牛们解答一下吧！！谢谢谢谢

牛牛们都在哪了呢？！

EVIDENCE:每个人买的东西的价格按照7%的百分比收税 CONCLUSION：收入越低，税的百分比越高

A：因为买东西的钱一样，所以买东西的税一样，所以对于收入低的人，一样的钱占他们的收入就多了

明白了，看来还是我句子的意思没弄明白！谢谢了